1. Field of the Invention
The present invention relates to a magnetic interface circuit, and particularly to a PoE (Power over Ethernet) magnetic interface circuit adapted for providing power supply and signals to an inner network.
2. Description of Related Art
A magnetic interface circuit is described in U.S. Pat. No. 7,123,117, which was issued on Oct. 17, 2006. The magnetic interface circuit comprises a transformer having a first winding connected to a line side of a LAN (Local Area Network) and a second winding connected to a circuit side of the LAN. The first and the second windings respectively have a pair of output ports. The first winding has a center tap port. A 3-wire CMC (Common Mode Choke) having a center winding and two outer windings. The center winding of the 3-wire CMC is connected to the center tap of the first winding. The outer windings of the 3-wire CMC are respectively connected to the output ports of the first winding. The magnetic interface circuit has a pair of DC (Direct Current) busses provided for a PoE port. When the magnetic interface circuit is supplied in a PoE system, the center taps of the 3-wire CMC are connected to a direct current power supply of a PSE (Powered Sourcing Equipment), via the DC busses. An inner network is connected to the direct current power supply of the PSE via the magnetic interface circuit to thereby form the PoE system. The magnetic interface circuit provides power supply from the direct current power supply to the inner network.
Polarity of the power supply provided by the magnetic interface circuit conforms with polarity of the direct power supply. When polarity of the direct power supply does not match with polarity of the inner network, the inner network could not get an available power supply from the magnetic interface circuit.
Hence, an improved magnetic interface circuit is required to overcome the above-mentioned disadvantages of the related art.